As the building blocks of proteins, amino acids give structure to your body. They play numerous additional roles—in healing, tissue repair and energy production. Some of the 20 amino acids that build body proteins are essential, meaning that you must get them from your diet. By contrast, your body can produce enough non-essential amino acids to meet its needs. Depending on the way your body metabolizes them, amino acids can also be classified as glucogenic, ketogenic or glucogenic-ketogenic.
Glucogenic and Ketogenic Amino Acids
As it does with carbohydrates and fats, your body metabolizes the amino acids in proteins to derive energy. Glucogenic amino acids yield glucose for energy production, whereas the body converts ketogenic amino acids into soluble compounds called ketone bodies via a process called ketogenesis. Ketogenic amino acids specifically form a type of ketone body known as acetoacetate, either directly or by first yielding the intermediary compound acetyl-CoA. Glucose is your body’s preferred energy currency, but ketone bodies provide an alternative fuel source when glucose is unavailable. There are seven ketogenic amino acids.
Lysine in an essential and exclusively ketogenic amino acid. It helps your body produce carnitine, a nutrient that metabolizes fatty acids into energy and helps to lower cholesterol. According to the University of Maryland Medical Center, lysine also helps with calcium absorption and the formation of collagen, the protein that makes your bones, cartilage, tendons and skin firm. Lysine breakdown ultimately yields the ketone body acetoacetyl-CoA for use in energy production. Lysine-rich foods include peas, lentils, beans, fish and meats.
Leucine is also an essential and exclusively ketogenic amino acid. Its breakdown produces acetyl-CoA and acetoacetate. Along with ketogenic amino acid isoleucine, leucine helps to produce energy in your muscles and promotes protein synthesis. TheMedicalBiochemistryPage.org also reports that leucine has a regulatory role in the chemical reactions that drive the weight loss effects of high-protein diets. Rich dietary sources of leucine are peanuts, salmon, beef, soybeans and lentils.
Glucogenic-Ketogenic Amino Acids
Biochemist Pamela C. Champe, Ph.D., names five amino acids whose breakdown ultimately yields glucose and ketone bodies. They are therefore both ketogenic and glucogenic. One of them, tyrosine, is non-essential and converts to acetoacetate during its breakdown. The other four are the essential amino acids threonine, isoleucine, phenylalanine and tryptophan. Isoleucine and leucine breakdown primarily occurs in your muscles, says Champe. By contrast, your liver metabolizes all the other amino acids.